Universal Mobile Telecommunications System (UMTS) networks have seen an explosive data growth in past few years and, in the future, are expected to see continuing growth in the Packet Switched (PS) domain. Beyond growth of data traffic volume, an even more aggressive growth in data signaling load has been detected. Among all the signaling messages/procedures on UMTS networks, Radio Access Network (RAN) signaling procedures have caused the most growth and impact. This is due to complicated radio resource sharing techniques required to conserve resources occupied by various users and services.
The majority of RAN signaling events are for connection setup and state transitions (e.g., during Channel Switching). Typically, when a data payload is to be sent from/received by a user equipment (UE), a request is sent to a radio network controller (RNC) to establish a dedicated channel (DCH). Once the data payload is sent or received, multiple inactivity timers are triggered by the RNC and upon expiration of the timers, the RNC transitions the UE from DCH to forward access channel (FACH) and then to IDLE state. To achieve resource efficiency, such timers are often set to short values (cumulatively around 12-16 seconds). Thus, the UE is quickly moved into the IDLE state after completion of a current data session (download and/or upload). Since there is no active data connection between the UE and the core network during the IDLE state, power consumption is minimized. However, if a new data payload is received shortly, a new data connection is requested and established between the UE and the RNC. As a result, even though battery life of the UE is conserved, a large number of signaling events are generated and RNC processing load is substantially increased.
In addition to network initiated inactivity-based state transition, UE manufacturers have introduced a fast dormancy (FD) feature that initiates direct transition from DCH to IDLE or FACH to IDLE, before the respective network inactivity timer expires. In this type of system control, the UE proactively releases the data connection, established by the RNC, directly from DCH to IDLE or FACH to IDLE as quickly as possible, to further conserve UE battery life. However, once the UE is in the IDLE state, the data connection must be reestablished to communicate another payload. The reestablishment of the data connection is resource intensive, consumes a high amount of power in the RNC, and can significantly drive up the RNC load.